The present invention relates in general to sewing fabrics together and, in particular to a new and useful device for sewing two workpiece plies together adjacent a contoured edge thereof.
To improve stability in the shape and comfort of trousers, the front parts of trousers are provided with a knee lining. This is done during the trimming of the longitudinal edges of the front parts of the trousers, by simultaneously sewing the lining piece or cut and securing the upper cut or piece of fabric with an overhead seam.
It is known, (German OS 2,747,792) to use sized lining cuts or pieces which register with the longitudinal edges of the upper fabric cuts. This requires the use of a number of lining pieces which are different in size and shape, to correspond to the variety of ready-made sizes and shapes of trousers.
Adequate care and time is needed for cutting the lining to sizes with exact contours. Another drawback is that the lining must be cut to size in an independent operation which is quite separate, in time and space, from the following sewing operation. This makes it also necessary to store both the upper fabric cuts and the lining cuts in the meantime, before the sewing operation. The time and space required therefor increase with the number of different ready-made sizes and designs.
To overcome these drawbacks, it has already been provided (German utility model 7,523,600) to replace contour-adjusted lining cuts with sized cuts of uniform width, for example rectangular ones, which fit the different sizes of the upper fabric cuts. During the sewing operation, the marginal portion of the lining cut, more or less protruding beyond the edge of the upper cut, is cut off by a cutting mechanism provided directly adjacent the stitch formation area of the sewing machine. To this end, the lining cut, along with the upper cut, must be advanced through the cutting area of the cutting mechanism in accordance with the contour of the upper cut. In such an operation, however, only the motion of the upper cut can be controlled by a contour controller. This control cannot be applied to the lining cut since the contour of the lining cut differs from that of the upper cut. Therefore, in such a case, the lining cut is not controlled in its advance, it is only taken along by frictional contact to follow the motion of the overlying upper cut which is moved laterally and rotated due to the contour control. Experience has shown however, that relative motions occur between the upper and lower cuts, which result in distortions of the lining cut and thus in an uneven and unsatisfactory product.